Can i get the balloons with helium in the store??

No my dear

No

The one in Fremont doesn't any more, you may want to call the store you're planning on going to make sure they still offer. I know Dollar Tree in Fremont has a nice variety. They have some blown up already and will fill right there also.

Yes you should be able to do that if they have a person available at the fabrics and crafts material department